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edd8e41d2e
The load balancer applies cpu_active_mask to whatever sched_domains it
finds, however in the case of active_balance there is a hole between
setting rq->{active_balance,push_cpu} and running the stop_machine
work doing the actual migration.
The @push_cpu can go offline in this window, which would result in us
moving a task onto a dead cpu, which is a fairly bad thing.
Double check the active mask before the stop work does the migration.
CPU0 CPU1
<SoftIRQ>
stop_machine(takedown_cpu)
load_balance() cpu_stopper_thread()
... work = multi_cpu_stop
stop_one_cpu_nowait( /* wait for CPU0 */
.func = active_load_balance_cpu_stop
);
</SoftIRQ>
cpu_stopper_thread()
work = multi_cpu_stop
/* sync with CPU1 */
take_cpu_down()
<idle>
play_dead();
work = active_load_balance_cpu_stop
set_task_cpu(p, CPU1); /* oops!! */
Reported-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20170907150614.044460912@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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|---|---|---|
| .. | ||
| autogroup.c | ||
| autogroup.h | ||
| clock.c | ||
| completion.c | ||
| core.c | ||
| cpuacct.c | ||
| cpuacct.h | ||
| cpudeadline.c | ||
| cpudeadline.h | ||
| cpufreq_schedutil.c | ||
| cpufreq.c | ||
| cpupri.c | ||
| cpupri.h | ||
| cputime.c | ||
| deadline.c | ||
| debug.c | ||
| fair.c | ||
| features.h | ||
| idle_task.c | ||
| idle.c | ||
| loadavg.c | ||
| Makefile | ||
| membarrier.c | ||
| rt.c | ||
| sched-pelt.h | ||
| sched.h | ||
| stats.c | ||
| stats.h | ||
| stop_task.c | ||
| swait.c | ||
| topology.c | ||
| wait_bit.c | ||
| wait.c | ||